I think the problem is that he was taken way too young from his parents (breeders NEVER pull them this young) and that he must have gone hungry for days before he got to you and, possibly, even after because parents feed all the time (they take turns but the baby gets food once every hour, more or less) when the babies are in the nest. Birds that are pulled too young from the nest or weaned incorrectly develop eating disorders and one of the symptoms is the screaming as well as the constant begging even when they are adults.

Well, I can tell you that the 'wait until the crop is empty to feed again' is wrong. The crop is only supposed to empty once a day (during the night). And I'll tell you more, baby birds often develop what is called 'slow crop' when fed incorrectly (wrong temperature, wrong consistency) and their crop would not empty for hours. Birds digest their food completely (from beak to poop) in two hours so, obviously, once every four hours is not often enough for such a young baby.

Like adopting a human child, you never really know what they have gone through. You can get a little info from the person who gave it to you but there are many things that that human did not know about him.

I think he has separation problems and wants to be with you all the time. The baggage that comes with them has to be learned. Even when getting a baby you just don't know how it was treated.

My daughter has a big boxer dog. When it first moved in with me he was happy to be with me. I would feed him twice a day and give him snacks between meals. He would be sweet and wagging his tail but as soon as I let go of his food bowl he would come at me. I think he was teased with food or just not fed enough. It was a year before he realized that he had a schedule and that food came on time.

You bird may have come with baggage you do not know of. You adopted him as a child. You need to try to understand his personality and fears. There is no quick fix for his problems.

I am sorry if it feels like I am nagging you. My 40+ kids tell me that all the time. I have never outgrown being a protective mother. So sorry it bothered you. I do know that I repeat myself and it feels like I am nagging.